House Democrats facing down tight deadlines and spiraling worries that President Biden’s agenda could soon fall apart are growing increasingly exasperated with a pair of Democratic senators whose votes are key but whose views are unclear when it comes to what they want out of legislation to expand the social safety net.

Sens. Joe Manchin III (W.Va.) and Kyrsten Sinema (Ariz.) have said Biden’s $3.5 trillion proposal for expanding heath care access, boosting education programs and fighting climate change is too expensive, but they have been reluctant to engage in detailed discussions about how they want it changed.

“We need to know what he’s a skeptic on so that we can have the conversation with him. There has been no clarity in what they actually want, both Sinema and Manchin,” said Rep. Ilhan Omar (D-Minn.), a member of the House Progressive Caucus.

Until they do, House liberals eager to enact the legislation say they are essentially banging their heads against the wall. House moderates, meanwhile, are wary of signing onto potentially politically fraught policies until they know whether they have the blessing of the senatorial pair and will make it into law.

“Should all of this just hinge on those two? Absolutely not. Because the question becomes, or the question is, who is their priority? What is their priority?,” Rep. Cori Bush (D-Mo.) said.

Those are the questions Democrats are asking as the House prepares for a possible vote Thursday on an infrastructure bill both Manchin and Sinema support but that liberals are promising to sink until they are given greater assurances that the separate social spending bill will also become law.

Given the 50-50 breakdown in the Senate, either Manchin or Sinema — who are sometimes referred to on Capitol Hill as Manchema — can sink any piece of legislation and, as the chamber’s most conservative Democrats, they are the toughest votes to secure on a range of issues favored by the party’s liberal base.

Late Wednesday, Manchin released the type of statement that has irritated large groups of Democrats in the past with its emphasis on slowing down and scaling back.

“At some point, all of us, regardless of party must ask the simple question — how much is enough?,” he wrote. Manchin didn’t provide more details on his views beyond concern over the package’s size, but he did emphasize that he wanted any new programs to have provisions that would establish limits on who could receive the benefits based on income.

“I assume he’s saying that the president is insane, because this is the president’s agenda,” Rep. Pramila Jayapal (D-Wash.), chair of the Progressive Caucus, said following Manchin’s statement. She added that his statement would only embolden liberals to vote against the infrastructure bill that is scheduled to be voted on Thursday in the House and that the West Virginian helped negotiate in the Senate. House liberals don’t oppose that bill but say they won’t let it pass until their top priority, the social spending package, is also on its way to becoming law.

Many Democrats said they would settle for Manchin and Sinema announcing a price tag for the bill that they could swallow so negotiations could begin on what to include in the legislation and what to cast aside.

“I think we just need them to say what’s the top line for them over there, which there’s always been some reticence about saying,” Rep. Richard E. Neal (D-Mass.), the chairman of the tax-writing Ways and Means Committee, said about how to proceed.

Manchin addressed some of these questions on Thursday when he told reporters he only supports up to $1.5 trillion in new spending. Sinema has not given any inclination of what she could support.

Manchin also responded to the anger directed at him by liberals by saying he’s not one and they shouldn’t expect him to rubber stamp their agenda.

“I’ve never been a liberal in any way, shape or form,” he said. “I don’t fault any of them who believe that they’re much more progressive and much more liberal. God bless ‘em. … For them to get theirs — elect more liberals.”

While Manchin often talks with reporters, puts out statements and writes op-eds, Sinema prefers to share as little as possible publicly and declines to answer reporters’ questions.

After raising the debt limit for decades, Republicans in recent years have leveraged it to enact spending cuts while also threatening government default. (JM Rieger/The Washington Post)

Further angering liberals is that while the duo have made increases in government debt a top concern, they have also expressed skepticism about raising taxes on corporations and the wealthy to offset the cost of the new spending, as many in the party want. Late Thursday, Manchin told reporters he supports some tax increases and also that he is interested in working on extending the child tax credit.

The annoyance with Manchin and Sinema is most pronounced, or at least publicly expressed, by House Democrats, but their Senate colleagues are running out of patience as well.

“Now it’s time I would say for both senators make your mark and close the deal. What is it that you want? What is your final goal? It’s time to stop talking around it and speak directly to it,” Sen Richard J. Durbin (D-Ill.) told CNN.

The lack of trust House liberals have in Manchin and Sinema has grown as time goes on and little progress is made.

Jayapal, in describing what it will take to convince her that the Senate is working in good faith on the social spending package and, accordingly, incline her and her caucus to vote for the infrastructure bill, echoed a phrase President Ronald Reagan used when he described his missile negotiations with Soviet leaders.

It “isn’t about trust. It’s just about verify,” she said.

She also places the blame for the current situation on a group of nine House Democratic moderates who pushed House Speaker Nancy Pelosi (D-Calif.) to hold a vote this week on the infrastructure bill in exchange for their votes on a budget blueprint that paved the way for the increased health care, education and climate change spending, saying they “called a new play” after there was an agreement the two bills would move in tandem.

“I think we’re in a situation where there’s a lot of needless hostage-taking. We can support everyone’s agenda here, and the idea that we must split them apart or have them on different dates is an artificial construct,” Rep. Alexandria Ocasio-Cortez (D-N.Y.) said.

A majority of House moderates, for their part, want to see the social spending bill pass and have tried to assuage their progressive counterparts that they will support it even if they vote for the infrastructure bill first, according to several sources in Tuesday’s Democratic caucus meeting who spoke on the condition of anonymity to describe the private meeting.

Moderates, including those in the most competitive districts, have worked with progressives to shape legislation that would make the child tax credit permanent and allow Medicare to negotiate prescription drug prices, two campaign promises the party ran on.

Rep. Susan Wild (D-Pa.), who is considered a vulnerable Democrat by the National Republican Campaign Committee, laid out the case for why House moderates are waiting on Manchin and Sinema due to worries they could vote for a policy that will be used against them on the campaign trail but does not make it into law.

“There’s a very strong sentiment among many of us, myself included, that we don't want to take a vote on something that isn't going to make it through the Senate. I mean what's the point of that? Why would we not wait? Not just politically, but it's just, it's a stupid way to proceed,” he said.

Progressives worry about voters’ reaction if the expansion of social safety net programs they ran on do not pass. Bush said that many of those Democratic voters who elected her to the House and Biden to the White House in 2020 may not vote for them next cycle because the party was unable to fully deliver on helping the less fortunate rise up economically.

“We cannot afford to lose the faith that so many voters have in this administration, in, in their elected officials right now when we say we would deliver,” she said.

While time is tight, some liberals expressed optimism that if Manchin and Sinema would provide more of their redlines and green lights that legislation could be quickly crafted — maybe even this week in some form.

“There’s always a chance here on Capitol Hill. Pigs fly here on Capitol Hill,” Jayapal said. “I have seen bills come together very quickly, and I’m doing everything I can to move the discussion forward on the reconciliation bill so that we can finalize that and finish that.”

Jacqueline Alemany contributed to this report.